Why this site exists
Buying a hat online is a small gamble. One brand sells a 7 ⅜, another sells an L, a third sells an S/M, and a European shop lists the same hat as a 59. Most size charts cover a single brand, give no centimetres, or leave out kids and babies. We built HatSizeCharts so that one measurement gives you a clear answer in every system, with the brand ranges side by side.
The site covers fitted caps, snapbacks, stretch-fit caps, cowboy and fedora hats, beanies, bucket hats, flat caps and graduation caps, plus sizing for men, women, kids, toddlers and babies. It also includes head circumference charts and a percentile calculator for babies and toddlers, and crochet and knitting size charts for people who make their own hats. Everything is available in eight languages.
Who we are
HatSizeCharts is a small independent project run by a team that writes and maintains reference tools. We are not a hat shop, we do not sell hats, and we are not affiliated with, sponsored by or endorsed by any of the brands mentioned on the site. Brand names such as New Era, Stetson, Nike, Flexfit, Richardson, Kangol, Carhartt and ’47 are trademarks of their owners and are used only to identify their products and size charts.
Where the numbers come from
Every figure on the site comes from a published source or from standard hatter’s arithmetic, and the same figures feed the tables, the calculators and the text, so they cannot drift apart.
- International conversion: a US fitted size is the head circumference in inches divided by pi, rounded to the nearest eighth. UK sizes run one eighth smaller than US sizes, and European and French sizes are the circumference in centimetres.
- Brand charts: each brand’s own published size guide (for example the charts on stetson.com, nike.com and neweracap.com). Where a brand prints rounded or inch-only values we keep the brand’s values rather than recalculating them.
- Adult head sizes: the ANSUR II anthropometric survey of more than 6,000 US Army personnel, which gives an average head circumference of 57.4 cm for men and 56.1 cm for women.
- Babies and toddlers: the WHO Child Growth Standards (birth to 24 months) and the CDC growth charts (24 to 36 months), using the published LMS parameters for the percentile calculator.
- Crochet and knitting: the Craft Yarn Council head circumference standards, with negative ease applied because knitted and crocheted fabric stretches.
How we check and update the charts
Brand size charts change without notice, so we re-check them against the brands’ own pages and correct the site when they change. We test the calculators across every measurement from 30 to 70 cm to make sure each result matches the tables on the same page, and we compare every translation against the English figures so that all eight language versions give the same numbers.
Size charts are a strong guide, not a guarantee. Hats from the same brand can fit differently by style, material and even batch, and head shape matters as well as circumference. When you are between two sizes, the site tells you so, and our general advice is to size up for fitted hats and check the retailer’s return policy.
Health information
The head circumference pages explain what the WHO and CDC reference charts show and how percentiles work. They are general information for parents, not medical advice. A single measurement outside the typical range, or a baby whose head size crosses percentile lines quickly, is something to discuss with a doctor or health visitor, who can measure accurately and look at the whole picture.
Advertising and independence
The site is free to use and has no sign-ups. To pay for hosting and upkeep it may show advertising, including ads served by Google AdSense. Advertisers have no influence over the size data or the advice on the site, and we do not accept payment to change a chart or recommend a brand. Details of cookies and advertising are in our privacy policy.
Corrections and contact
If a brand has updated its chart, a figure looks wrong, or a translation reads badly, please tell us. Corrections are reviewed quickly and fixed on every language version at once. You can reach us at [email protected] or through the contact page.